Optical navigation sensors are conventionally used for surface navigation devices, such as an optical mouse for desktop computers. In general, an optical navigation device tracks the relative movement between the navigation surface and the sensor within the navigation device.
More recently, optical finger navigation devices have been widely used in many handheld portable devices to provide a navigation function by finger operation. In contrast to a conventional optical mouse system, an optical finger navigation device uses a light source to illuminate a user's finger and a sensor to generate the images from light that is reflected off the user's finger. The general operational concept of an optical finger navigation device is somehow similar to a conventional optical mouse, except that the sensor incorporated in for finger navigation is generally positioned facing upward from the device, rather than downward. In addition, the tracking surface for the optical finger navigation system is a user's finger, rather than a desktop work surface. Accordingly, an optical finger navigation device translates the movement of a finger into movement of a cursor on a display of a corresponding handheld portable device. Whereas a conventional optical navigation system translates the movement of a mouse over a work surface into the movement of a cursor on a computer display.
An optical navigation system can be effectively used in many small portable devices such as cell phone, PDAs, etc. However, as the size of such a device continues to be reduced and becomes more compact in design, the optical navigation device is allotted a smaller and smaller footprint for assembly and operation. Accordingly, the overall package size and the height of the optical navigation device must continue to shrink. Hence it has become difficult to produce such small optical finger navigation systems for use in compact portable devices. As the package size becomes smaller, the manufacturing process of optical finger navigation devices inevitably becomes more complex and expensive. Therefore, a small profile optical navigation device that can be manufactured easily and more inexpensively is desirable. In addition, an optical navigation device with fewer component parts that would enable reduced assembly and raw material component costs is desirable.